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Stem cell shots restore lost memory
08 November 2007
From New Scientist Print Edition.
Andy Coghlan

Stem cell injections might restore memory lost through strokes, Alzheimer's and other neurodegenerative diseases - at least that's what experiments in mice suggest.

In previous studies transplanted neural stem cells survived and integrated into brain circuitry, says Mathew Blurton-Jones, a member of the team carrying out the experiments at the University of California at Irvine. "We've now gone one stage further in showing that once integrated, these new neurons are able to reverse cognitive deficits associated with neurodegeneration or neuronal loss," he says.

After the team had destroyed memory cells in the hippocampuses of mice, they performed badly in a standard memory test compared to healthy animals. Both sets of mice were placed in enclosures containing two identical objects a few centimetres apart. Then the mice were taken away and one of the two objects was moved into a different position. When the mice went back into their enclosure, the healthy mice spent much more time investigating the moved object, whereas the brain-damaged mice spent equal time investigating both, showing they hadn't registered that one had been moved.

When the researchers injected neural stem cells from newborn mice into the hippocampuses of the damaged mice, they recognised when an object had been moved. They also had elevated levels of synapsin, an enzyme which promotes connections between brain cells.

Recovery wasn't immediate, taking around three months (Journal of Neuroscience, DOI: 10.1523/JNEUROSCI.1627-07.2007). "This [time delay] suggests that the transplanted cells must mature sufficiently and make all the right connections within the hippocampus before they can reverse the deficits," says Paul Frankland, who studies memory formation at the research institute of the Hospital for Sick Children in Toronto, Canada. His own experiments have shown that adult-generated neurons need to mature for at least six weeks before they begin to contribute to memory formation.

Blurton-Jones's team says the mouse results are the first evidence that stem cells might reverse cognitive damage, although they stress that much more animal work is needed before they can move on to humans. The next step is to test the stem cells in mice with an Alzheimer's-like disease.

Meanwhile, ReNeuron, based in Guildford, UK, is hoping to get approval from the US Food and Drug Administration to treat 10 stroke patients with human neural stem cells before the end of the year. "This paper is encouraging, and certainly supportive of endeavours in this field, including ours," says ReNeuron's Michael Hunt.

From issue 2629 of New Scientist magazine, 08 November 2007, page 10

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